This invention relates to an electron beam exposure apparatus and method of controlling the same. More particularly, the invention relates to an electron beam exposure apparatus for drawing a pattern on a wafer directly or on a mask or reticle using a plurality of electron beams, a method of controlling the apparatus, the associated control program and a method of manufacturing a device using this electron beam exposure apparatus.
Examples of electron beam exposure apparatuses include an apparatus of the point beam type which uses a beam in the shape of a spot, an apparatus of the variable rectangular beam type which uses a beam in the shape of a rectangular cross section, and an apparatus of the stencil mask type which uses a beam given a desired cross-sectional shape through use of a stencil mask.
The electron beam exposure apparatus of the point beam type is used exclusively for research and development purposes because of its low throughput. Though the electron beam exposure apparatus of the variable rectangular beam type has a throughput higher than that of the apparatus of the point beam type by one to two orders, many problems remain in terms of throughput when it is attempted to expose a pattern consisting of fine patterns on the order of 0.1 .mu.m integrated to high density. On the other hand, the electron beam exposure apparatus of the stencil mask type uses a stencil mask in which a plurality of repetitive pattern through-holes are formed at a portion thereof that corresponds to a variable rectangular aperture. As a result, the electron beam exposure apparatus of the stencil mask type is highly advantageous when exposing repetitive patterns. However, in the case of a semiconductor circuit that requires a multiplicity of transfer patterns that will not fit on a single stencil mask, it is necessary to produce a plurality of stencil masks in advance and use them by extracting them one at a time. Since changing masks takes time, a problem that arises is a very low throughput.
An apparatus which solves this problem is a multi-electron beam exposure apparatus which irradiates the surface of a sample with a plurality of electron beams along design coordinates of the surface, scans the plurality of electron beams across the sample surface by deflecting the electron beams along the design coordinates, and turns the plurality of electron beams on and off individually in conformity with the pattern to be drawn, thereby drawing the pattern on the surface. A feature of the multi-electron beam exposure apparatus is that throughput can be improved owing to the ability to draw any pattern without using a stencil mask.
FIG. 15 illustrates the general arrangement of the multi-electron beam exposure apparatus. The apparatus includes electron guns 501a, 501b, 501c whose electron beams can be turned on and off individually, a reduction electron optical system 502 for reducing the diameters of the plurality of electron beams and projecting the beams upon a wafer 503, and a deflector 504 for scanning the plurality of projected electron beams of reduced diameter across the wafer 503.
FIG. 16 illustrates the manner in which the plurality of electron beams are scanned across the surface of the wafer. The white circles in FIG. 16 are beam reference positions (BS1, BS2, BS3) at which the electron beams impinge upon the wafer when they are not deflected by the deflector 504. The beam reference positions are arrayed in a design rectangular coordinate system (Xs, Ys). Each electron beam is scanned in the design rectangular coordinate system (Xs, Ys) using the beam reference position as a reference, thereby scanning exposure fields EF1, EF2, EF3 of the respective electron beams. The wafer is exposed using the contiguous exposure fields of the electron beams.
When a deflection coordinate system (Xd, Yd) decided by the deflector is offset from the design rectangular coordinate system (Xs, Ys), however, the exposure fields of the electron beams come to overlap or separate, rather than remain contiguous, even through the beam coordinate system (Xa, Ya) decided by the plurality of beam reference positions coincides with the design rectangular coordinate system (Xs, Ys). This makes it impossible to draw the desired patterns. FIG. 17A illustrates the exposure fields in a case where the deflection coordinate system has been rotated with respect to the beam coordinate system. FIG. 17B illustrates the exposure fields in a case where the deflection coordinate system has been enlarged with respect to the beam coordinate system.